1. Field of the Invention
The present invention relates to a noise-cut filter for an electric power converter such as an inverter, which filters switching noises generated with switching actions of semiconductor switching devices of the electric power converter.
2. Description of Related Art
The switching actions of the semiconductor switching devices of the electric power converter such as the inverter are taken according to pulse-width modulated (PWM) drive signals with a carrier frequency of several kHz or less than about twenty kHz. As a result of the switching actions, the electric power converter generates switching noises of frequency components of dozens of kHz or higher.
In recent years, the electric power converter is regulated by a variety of laws in order to reduce a harmful influence of components of 100 kHz or higher among frequency components of the switching noises upon external equipment. Accordingly, the electric power converter is provided with a noise-cut filter.
The conventional noise-cut filter for the electric power converter is constructed by connecting a single reactor, in which electric wire is wound on a core made of ferrite, amorphous alloy, crystal alloy or the like, with a single condenser made of film, chip, or the like in, for example, an inverted L-shape. This noise-cut filter filters the switching noises generated with the switching actions of the semiconductor switching devices.
The reactor used as the conventional noise-cut filter is ordinarily troidal, and the condenser is flat, cylindrical or the like in order to be inserted through a pin. When they are mounted on a printed circuit board inside the electric power converter, they require a larger mounting space than the volume thereof. Moreover, if the filter is mounted by separate wiring, there are too many parts to be connected and it is complicated to fix each part.
It is therefore an object of the present invention to provide a small and thin noise-cut filter for an electric power converter at low costs.
The first embodiment of the present invention is a noise-cut filter comprising: a spiral LC composite member in which a desired number of rectangular dielectric chips are bonded together in a state of being put between two spiral coils having rectangular sections; a noise-cut filter circuit, in which a desired number of layers of the spiral LC composite members are laminated through insulation sheets, and one spiral coils of the spiral LC composite member are connected at inside ends thereof to form main circuits for carrying a desired current, and the other spiral coils of the spiral LC composite members are connected at inside ends thereof to form earth circuits for carrying a current resulting from to a high frequency noise; a noise-cut filter circuit laminate in which a desired number of the noise-cut filter circuits are laminated through insulation sheets; and a filter circuit which is formed by enclosing the center and outer peripheral part of the noise-cut filter circuit laminate by a magnetic body in such a manner as to form magnetic circuits, the filter circuit functioning as a reactor and a condenser.
The second embodiment of the present invention is a noise-cut filter of the first embodiment, wherein the spiral coils are formed by pressing and stamping out a metal plate to a predetermined thickness.
The third embodiment of the present invention is a noise-cut filter of the first embodiment, wherein: the spiral coils of the main circuits are formed by pressing and stamping out a metal plate to a predetermined thickness, and the spiral coils of the earth circuits are of the same shape as the spiral coils of the main circuits except for thickness and are formed by pressing and stamping out a thin metal plate having a section for carrying a desired current.
The fourth embodiment of the present invention is a noise-cut filter of the first embodiment, wherein the spiral coils of the main circuits are formed by pressing and stamping out a metal plate to a predetermined thickness, and the spiral coils of the earth circuits are made of a printed circuit board formed by etching a copper foil in the same planar pattern as the spiral coils of the main circuits.
The fifth embodiment of the present invention is a noise-cut filter of the first embodiment, wherein the spiral coils of the main circuits are formed by pressing and stamping out a metal plate to a predetermined thickness, and the spiral coils of the main circuits are formed by coating conductive paste material of the same plane pattern as the spiral coils of the main circuits on insulation sheets, the earth circuit functioning as a resonance control resistance.
The sixth embodiment of the present invention is a noise-cut filter of one of the first through sixth embodiments, wherein conductive paste material is coated on surfaces of the rectangular dielectric chips, which are bonded with the spiral coils in advance, and the dielectric chips and the spiral coils are bonded together through conductive adhesive material.
The seventh embodiment of the present invention is a noise-cut filter of one of the first through fifth embodiments, wherein conductive paste material is coated on surfaces of the rectangular dielectric chips, which are bonded with the spiral coils in advance, and the dielectric chips and the spiral coils are bonded together through solder material.
The eighth embodiment of the present invention is a noise-cut filter of one of the first through fifth embodiments, wherein conductive paste material is coated on surfaces of the rectangular dielectric chips, which are bonded with the spiral coils in advance, and the dielectric chips and the spiral coils are bonded together through resin material.
The ninth embodiment of the present invention is a noise-cut filter of one of the first through eighth embodiments, wherein a filter unit is constructed by containing a noise-cut filter of any one of claims 1 through 8 in a plastic case, which is sealed with resin material.
The tenth embodiment of the present invention is a noise-cut filter unit of the ninth embodiment, wherein the resin material is made of high polymer resin material that is filled by an inorganic filler by a predetermined percentage.
The eleventh embodiment of the present invention is a noise-cut filter unit of one of the first through eighth, wherein a filter unit is constructed by containing a noise-cut filter of any one of the first through eighth embodiments 1 through 8 in a plastic case; sealing other area in the plastic case by the silicon gel; and sealing only an area at a side, where input/output terminals are arranged, by a high-polymer resin material that is filled by an inorganic filter by a predetermined percentage.
The twelfth embodiment of the present invention is a noise-cut filter unit as defined of the ninth embodiment, wherein the resin material is comprised of silicon gel, and a cover is provided in an area where input/output terminals are arranged in order to fix the terminals.
The thirteenth embodiment of the present invention is an electric power converter wherein a noise-cut filter of any one of the first through eighth embodiments or a noise-cut filter of one of the ninth through twelfth embodiments is connected to an input stage and/or an output stage of the electric power converter having switching devices to thereby form common mode choke coils, thus filtering switching noises generated with switching actions of the switching devices.
The fourteenth embodiment of the present invention is an electric power converter, wherein a noise-cut filter of one of the first through eighth embodiments or a noise-cut filter of one of the ninth through twelfth embodiments is connected to circuits in the electric power converter having switching devices to form common mode choke coils, thus filtering switching noises generated with switching actions of the switching devices.